Assembly and method for use in terminating an optical fiber or fibers

ABSTRACT

An assembly for use in terminating an optical fibre comprises an outer body ( 10 ), a first member ( 11 ) locatable in the outer body ( 10 ) and which carries a protruding length of optical fibre ( 36 ) which locates an alignment means ( 44, 45 ) and a housing ( 12 ) locatable in alignment with the first member ( 11 ). The housing ( 12 ) has an access opening for receiving an optical fibre ( 52, 53 ) to be terminated so that the fibre can be located in the alignment means in abutment with the optical fibre length ( 35 ). The housing has a compartment ( 47 ) which receives a heat responsive adhesive element ( 57 ), a saddle ( 58 ) and a resistor ( 59 ). when a current is passed through the resistor, the heat generated is transmitted by the saddle to the adhesive which melts and flows around the optical fibre ( 52, 53 ) to secure it in position in abutment with the optical fibre length ( 35 ).

This invention relates to an assembly for use in terminating an opticalfibre or optical fibres.

[0001] The use of optical fibres as a signal-carrying medium forcommunications is now extremely widespread and continues to increase.Optical fibres are used not only in cables which interconnectgeographically separated locations, but also within buildingsthemselves. As such there is a need for an optical fibre terminationwhich can be used in the field in order to terminate an optical fibre orfibres.

[0002] According to a first aspect of the present invention there isprovided an assembly for use in terminating an optical fibre comprisinga housing which can receive the optical fibre to be terminated so thatit is located in alignment with a length of another optical fibre, or anoptoelectronic device, said housing including a compartment throughwhich the optical fibre to be terminated can extend, said compartmentbeing designed to receive a heat responsive adhesive element and athermally conductive element, which can be coupled to a source of energyso that heat in the thermally conductive element causes the adhesive tomelt and flow around the optical fibre to secure it in position.

[0003] According to a second aspect of the present invention there isprovided an assembly for use in terminating an optical fibre comprisingan outer body member, a first member locatable within said body member,said first member carrying a length of optical fibre which protrudestherefrom, a housing locatable in alignment with the first member, anoptical fibre alignment means for receiving the end of the length ofoptical fibre which protrudes from the first member, said housing havingan access opening for receiving an optical fibre to be terminated sothat said fibre can be located in the alignment means so as to bealigned and abutted with the optical fibre length, said housingincluding a compartment through which the optical fibre to be terminatedextends, said compartment being designed to receive a heat responsiveadhesive element and a thermally conductive element, which can becoupled to a source of energy so that heat in the thermally conductiveelement causes the adhesive to melt and flow around the optical fibre tosecure it in position. By heat responsive adhesive is meant a materialwhich in the presence of heat can assume a condition in which it canflow or be caused to flow and subsequently harden again on cooling inorder to secure an optical fibre in position.

[0004] The compartment may accommodate said heat responsive adhesive,said thermally conductive element, and an electrically conductiveelement.

[0005] The compartment may accommodate said heat responsive adhesive andsaid thermally conductive element, access to said compartment beingprovided for a heat source. The electrically conductive element may be aresistor.

[0006] The thermally conductive element may be a metallic element. Thethermally conductive element may be a saddle which straddles theadhesive element.

[0007] The outer body member may include one or more openings so locatedas to allow connection of an electrical power source to saidelectrically conductive element or thermal contact to an external heatsource.

[0008] The plug assembly may be used to terminate more than one opticalfibre. The assembly may include a plurality of optical fibre alignmentelements. The alignment element or elements may comprise a sleeve orsleeves, a V groove or grooves, ceramic or metal ferrules, glasscapillary triple rod aligners or a combination of these.

[0009] A third aspect of the present invention provides a method ofterminating an optical fibre or fibres using an assembly according toany preceding claim, which comprises positioning the end of an opticalfibre to be terminated in said housing so it is in alignment with thelength of the other optical fibre, or optoelectronic device, heatingsaid thermally conductive element such that the adhesive assumes thestate in which it can flow around the optical fibre to be terminated andsecured in position in alignment with the optical fibre length.

[0010] The invention will be described now by way of example only, withparticular reference to the accompanying drawings. In the drawings:

[0011]FIG. 1 is an exploded view of an assembly in the form of a plugassembly in accordance with an embodiment of the present invention;

[0012]FIG. 2 is a perspective view of the plug assembly;

[0013]FIG. 3 is a side elevation of the plug assembly;

[0014]FIG. 4 is a section on the line 4-4 of FIG. 3;

[0015]FIG. 5 is a sectional view on the line 5-5 of FIG. 3;

[0016]FIG. 6 is a perspective view showing a modification of a componentin the plug assembly of FIG. 1;

[0017] FIGS. 7 to 10 show a modification of the embodiment of FIG. 1,and

[0018]FIG. 11 shows a modified form of saddle.

[0019] Referring to FIGS. 1 to 5 a plug assembly for use in terminatingan optical fibre or optical fibres comprises an outer body member (10),a first member part (11) and a housing part (12). These parts can all bemoulded from suitable plastics materials.

[0020] The outer body member has a body portion (14) which definestherein a space of generally rectangular cross-section which can receivethe first member (11). Two opposite side walls of the body portion (14)each have an aperture (16) formed therein at a generally centrallocation. The open end of the body portion (14) has four longitudinallyextending slots identified by reference number (18), the slots beingarranged so that one is formed in each of the walls of the body portion(14).

[0021] The internal surface of the body portion (14) is formed with astep (20) which is illustrated in FIG. 5 of the drawings. The top wallof the body portion (14) can have a transparent section (19).

[0022] The other end of the outer body member (10) has an enlargedportion (21) which is formed integrally with the body portion (14). Inthe top wall of the enlarged portion (21) are formed two spaced throughholes (22). Internally, as shown in FIG. 4, opposite side walls of thebody portion (21) have steps shown at (54). The lower wall of theportion (21) has an integrally formed resilient catch element (25) whichcan be used to secure the plug assembly in another part of an opticalfibre connector in a manner which will be apparent to those skilled inthe art.

[0023] The first member (11) comprises a main body portion (30) ofgenerally rectangular cross-section and an end portion (31) whosedimensions are slightly greater than the body portion (30) so that astep (32) is formed around their junction. The first member (11) hassecured therein a pair of optical fibre lengths (35) which at one endare substantially flush with an end face (36) of the first member and atthe other end protrude from the end portion (31) as illustrated inFIG. 1. Also the first member (11) has two longitudinally extendingbores formed therein, these extending for the full length of the body.The housing part (12) has a first generally channel-shaped section (40)from one end of which projects a pair of spaced pins (41, 42). Thechannel section (40) defines a compartment (43) which can receive a pairof optical fibre alignment elements in the form of a pair of guidesleeves (44, 45) which preferably are optically transparent. Each guidesleeve has a through bore with a diameter corresponding to that of anoptical fibre. The ends of each bore are widened to facilitate insertionof an optical fibre. One side wall of the channel-shaped section has anoutwardly extending projection (38).

[0024] The housing part (12) also includes an end housing part (46)which is formed integrally with the channel-shaped section (40). The endpart (46) defines a compartment (47). The lower surface of thecompartment (47) defines two side-by-side grooves (48, 49) in which canlocate the protective outer sleeves (50, 51) of two optical fibres (52,53), which are to be terminated. The outer surface of opposite sidewalls of the end part (46) are stepped at (24). The end wall (55) of theend part (46) has formed therein an aperture (56). The compartment (47)can accommodate above the optical fibres (52,53) and sleeves (50,51) aheat responsive adhesive in the form of a glue pellet (57) which isstraddled by a thermally conductive saddle (58) on top of which islocated an electrical resistor (59) which has conductive pads (60, 61).The saddle may be formed from aluminium or other suitable thermallyconductive material.

[0025] In order to assemble the plug assembly the pins (41, 42) on thehousing part (12) are located within the longitudinally extending boresformed in the first member (11), the housing part (12) is moved towardsthe first member (11) and the protruding parts of the optical fibres(35) locate into one end of the sleeves (44, 45), which sit within thecompartment (43) of the housing part (12).

[0026] The assembly of the glue pellet (57), the saddle (58), and theresistor (59) are located in the compartment (47) as shown in FIG. 4 ofthe drawings. The first member (11) and housing part (12) are moved intothe outer body member (10) so that they assume the position shown inFIG. 5 of the drawings. It will be noted that this movement is arrestedwhen the step (32) on the first member (11) comes into contact with thestep (20) formed on the interior surface of the outer body member (10).Also at this point the projection (38) on the channel-shaped section(40) locates within the opening (16) to secure the body parts inposition. The step (24) on the outer surface of the end part (46) sitson the step (54) on the interior of the body portion (21).

[0027] In use the optical fibres to be terminated are fed through theaperture (56) in the end wall (55) into the compartment (47) so that theouter sleeves (50, 51) of the fibres sit within the grooves (48, 49) atthe base of that compartment. The optical fibres (52, 53) which protrudefrom the sleeves (50, 51) are fed into the end of the sleeves (44, 45)until they meet and abut with the optical fibre lengths at a positionshown at (65) in FIG. 5.

[0028] Optical radiation is then passed through the optical fibres (52,53) and the junction of the fibres (52, 53) with the optical fibrelengths (35) is detected through the transparent section (19) of thebody member (10). If radiation is detectable, this is an indication thatthe fibres (52, 53) and optical fibre lengths (35) are not alignedand/or abutted correctly. They are then manipulated until the radiationis substantially extinguished indicating correct abutment and/oralignment. At this point an electrical power source is connected to thepads (60, 61) of the resistor by passing electrical conductive terminalsof the power source through the apertures (22) formed in the portion(20) of the outer body member (10) so that they contact the pads (60,61). Electrical current is passed through the resistor (59) which heatsup the glue pellet (57) by way of the thermally conducting saddle (58).The power source is in the form of a tool which can be used to applypressure to the resistor and hence the adhesive in order to cause it toflow around the fibres. The adhesive melts and flows around the opticalfibres (52, 53). The thermally conducting saddle has a good thermalconductive bond with the resistor (59). When the current is interruptedthe adhesive then resets to secure the fibres (52, 53) in their correctposition in alignment and abutment with the optical fibre lengths (35).

[0029] It will be appreciated that the above described plug assemblyrepresents a very convenient way of terminating optical fibres in thefield since it is relatively simple to use.

[0030] The plug assembly as described above is used to terminate a pairof optical fibres. It will be appreciated that the assembly can be usedto terminate one or several optical fibres. Also the assembly asdescribed includes a single compartment (47) for receiving the adhesivepellet. It will be appreciated that assemblies can be constructed whichhave more than one compartment.

[0031] Also the assembly as described is used to terminate opticalfibres so that they are aligned with optical fibre lengths (35). It willbe appreciated that the basic principle of activating a heat responsiveadhesive by heating it using an electrically conductive element can beapplied generally to many different types of optical fibre splice orconnector and not just that described in the above embodiment.

[0032] An alternative form of saddle and resistive heating element isshown in FIG. 6 of the drawings. In this arrangement the resistor andsaddle are effectively combined into a single element.

[0033] The arrangement shown in FIG. 6 comprises a U-shaped member (80)which is formed from ceramic material and which, in use, straddles theglue pellet (57) in much the same way as the saddle (58) of FIG. 1.

[0034] A pair of conductive contacts (82, 83) are formed on the uppersurface of the U-shaped member (80) and a resistive element (85) extendsaround the upper surface between the contacts (82, 83).

[0035] In use the arrangement operates in a manner similar to thatdescribed for FIGS. 1 to 5. Electrically conductive terminals of a powersource are passed through the apertures (22) of the portion (21) so thatthey contact the contacts (82, 83) on the U-shaped member (80).Electrical current from the power source is then passed through theresistive element (85) and the heat generated is conducted through theU-shaped member (80) and melts the glue pellet which then flows aroundthe fibres (52, 53).

[0036] In the embodiment described with reference to FIGS. 1 to 5 thealignment means for the fibre lengths (36) and the fibres (52, 53) aresleeves (44, 45).

[0037] It will be appreciated that other alignment means can beemployed. One example is a V-groove type arrangement which is employedin an alternative embodiment illustrated in FIGS. 7 to 10. The connectorshown in these Figures is similar to that of FIGS. 1 to 5, but thealignment is achieved using a pair of V-grooves (90, 91) formed in acomponent (92). The component (92) is located over the fibre ends to bealigned and abutted which are located on the base of the compartment(43). Each pair of fibres extends along one of the grooves (90, 91) in amanner which will be apparent to those skilled in the art. The component(92) is retained in position in the channel-shaped section (40) by aclip (94).

[0038] Other differences with respect to the first embodiment are thelocation of the aperture (16) and cooperating projection (38), theprovision of slots (95) rather than holes (22) for the terminals orelectrodes of the power source, and the provision of a cable clamp (96).

[0039] In the arrangements described above the resistor is accommodatedin the compartment (47). It is possible to produce an embodiment inwhich the resistor is external to compartment. One example isillustrated in FIG. 11. In this arrangement the saddle is formed with athicker upper part (98) so that when located in the compartment (47) itsupper surface is substantially flush with the upper edges of the walls.of the compartment (47). In this example the body part (21) will have arectangular opening corresponding in shape to the top surface of thesaddle, instead of the holes (22).

[0040] In use an external resistor, which will be part of the powersource, is located in that rectangular opening so that it rests againstthe upper surface of the saddle. When a current is passed through theresistor the adhesive is heated substantially as described before.

[0041] Alternatively the power source can be provided with a coil whichcan be located against or near the saddle to heat the saddleinductively.

[0042] It will be appreciated that the embodiments described are MTRJtype connectors. The basic principle of using a heat responsive adhesivein conjunction with a thermally conductive element such as saddle (58)can be employed in other types of connector such as SC, LC, ST, LX5, MU,MTP, E200 connectors.

1. An assembly for use in terminating an optical fibre comprising ahousing which can receive the optical fibre to be terminated so that itis located in alignment with a length of another optical fibre, or anoptoelectronic device, said housing including a compartment throughwhich the optical fibre to be terminated can extend, said compartmentbeing designed to receive a heat responsive adhesive element and athermally conductive element, which can be coupled to a source of energyso that heat in the thermally conductive element causes the adhesive tomelt and flow around the optical fibre to secure it in position.
 2. Anassembly for use in terminating an optical fibre comprising an outerbody member, a first member locatable within said body member, saidfirst member carrying a length of optical fibre which protrudestherefrom, a housing locatable in alignment with the first member, anoptical fibre alignment means for receiving the end of the length ofoptical fibre which protrudes from the first member, said housing havingan access opening for receiving an optical fibre to be terminated sothat said fibre can be located in the alignment means so as to bealigned and abutted with the optical fibre length, said housingincluding a compartment through which the optical fibre to be terminatedextends, said compartment being designed to receive a heat responsiveadhesive element and a thermally conductive element, which can becoupled to a source of energy so that heat in the thermally conductiveelement causes the adhesive to melt and flow around the optical fibre tosecure it in position.
 3. An assembly according to claim 1 or claim 2,wherein said compartment accommodates said heat responsive adhesive,said thermally conductive element, and an electrically conductiveelement which is so mounted that when an electrical current is passedthrough the electrically conductive element the heat in the thermallyconductive element melts the adhesive.
 4. An assembly according to claim1 or claim 2, wherein said compartment accommodates said heat responsiveadhesive and said thermally conductive element, access to saidcompartment being provided for a heat source to be coupled with thethermally conductive element.
 5. An assembly according to claim 3,wherein said electrically conductive element is a resistor.
 6. Anassembly according to any preceding claim, wherein the thermallyconductive element is a metallic element.
 7. An assembly according toany preceding claim, wherein the thermally conductive element is asaddle which straddles the adhesive element.
 8. An assembly according toclaim 1 or claim 2, wherein the source of energy is an induction coilcarried by a suitable tool.
 9. An assembly according to claim 1 or claim2, wherein the thermally conductive element is a ceramic saddle which isprovided with resistive portions to which an electrical current can beapplied.
 10. An assembly according to any one of claims 2 to 9, whereinthe outer body member includes one or more openings so located as toallow either connection of an electrical power source to saidelectrically conductive element, or the application of an externalenergy source.
 11. An assembly according to any preceding claim, whichis arranged to terminate more than one optical fibre.
 12. An assemblyaccording to claim 10, including a plurality of compartments forreceiving the adhesive element.
 13. A method of terminating an opticalfibre or fibres using an assembly according to any preceding claim,which comprises positioning the end of an optical fibre to be terminatedin said housing so it is in alignment with the length of the otheroptical fibre, or optoelectronic device, heating said thermallyconductive element such that the adhesive assumes the state in which itcan flow around the optical fibre to be terminated and secured inposition in alignment with the optical fibre length.
 14. A methodaccording to claim 13, including sensing alignment of the optical fibreto be terminated with the optical fibre length by passing radiationalong the fibres and observing the level of radiation detectable at thejunction of the optical fibre and the optical fibre length.